Magnetic separation apparatus

ABSTRACT

A magnetic separation device, with streamlined construction and heightened rate of magnetic adhesion, has two rotating plates  7, 8  which are fixed to a rotation axis and rotate while immersed in a liquid, and magnets  13  mounted on the rotating plates  7, 8.  The magnetic separation device is constructed such that magnetic material in the liquid magnetically adheres to the rotating plates  7, 8  and is separated. Further, the magnetic separation device includes a yoke  14,  surrounding and accommodating magnets, and having an aperture facing one of the magnetic poles; the yoke  14  has an aperture side face  14   c  which is in contact with the rotating plates  7, 8;  and the aforementioned magnetic pole is in contact with the rotating plates  7, 8.  Pairs of magnets  13  are arranged such that opposite magnetic poles oppose each other across the two rotating plates  7, 8,  and a magnetic space is formed between the two magnetic plates  7, 8.

FIELD OF THE INVENTION

[0001] This invention relates to a magnetic separation device whichseparates material suspended in a liquid using magnetic force.

BACKGROUND OF THE INVENTION

[0002] A magnetic separation device is a device which separates materialsuspended in a liquid using magnetic force. Because there is no need tochange filters in a magnetic separation device, separation of suspendedmaterial can be performed continuously without interruption.Consequently, maintenance of a magnetic separation device is easy.

[0003] The Japanese Patent Application Laid-Open No. Hei 9-248483,published by Japan in 1997, and the Japanese Patent ApplicationLaid-Open No. Hei 10-244424, published by Japan in 1998, disclose amagnetic separation device, comprising a pair of rotating plates whichrotate while submersed in the liquid and a pair of magnets mounted so asto oppose each of the rotating plates, and which separates materialsuspended in the liquid by magnetic adhesion to the rotating plates.

[0004] Japanese Patent Application Laid-Open No. Hei 9-248483 disclosesa magnetic separation device comprising a yoke 42 formed in a “U” shape,connecting the rear surfaces of two magnets 41 in mutual opposition, asshown in FIG. 7. In this magnetic separation device, when the magnets 41provided as a pair are within the range over which the magnetic actionof one magnet extends to the other magnet, a magnetic circuit isconstituted within the yoke 42, and a strong magnetic field occursbetween the magnets 41. As a result, the rate of magnetic adhesion ofsuspended material is increased.

[0005] However, in this device, if the magnets 41 provided in a pair areremoved to a distance from each other so that the magnetic action fromone magnet does not extend to the other magnet, as shown in FIG. 8, amagnetic circuit is not constituted within the “U”-shaped yoke 42.Consequently the magnetic field created between the magnets 41 isweakened, similarly to the case of separate individual magnets, and therate of magnetic adhesion of suspended material is reduced.

[0006] Also, because a plurality of “U”-shaped yokes 42, each providedwith a pair of magnets 41, are positioned parallel to the shaft ofrotation of a rotating plate, the product cost tends to be increased,and the increased weight of movable parts tends to result in increasedrunning costs.

SUMMARY OF THE INVENTION

[0007] Hence an object of this invention is to provide a magneticseparation device with a simple construction and enabling high rates ofmagnetic adhesion.

[0008] In order to attain the above object, this invention provides amagnetic separation device comprising two rotating plates which arefixed to a rotation shaft and rotate while immersed in liquid, and aplurality of magnets mounted on each of the rotating plates, and whichcauses material suspended in the liquid to magnetically adhere to eachof the rotating plates and to be separated from the liquid.

[0009] In this magnetic separation device, each of the above magnets isprovided with a yoke enclosing the magnet, and having an aperture facingone magnetic pole of the magnet. The yoke comprises an aperture sideface, which contacts one of the two rotating plates together with themagnetic pole. A pair of magnets is positioned such that oppositemagnetic poles face each other across two rotation plates, so that amagnetic space is formed between the two rotating plates.

[0010] More preferably, a “U”-shaped groove is formed in the apertureside face of the above yokes. Still more preferably, the magneticseparation device comprises a scraper which scrapes away magneticmaterial adhering to the above rotating plates, a mechanism whichrotates the above scraper in synchronization with the above rotatingplates, and means for guiding such that the above liquid flows in theabove magnetic space. It is also preferable that the surfaces of theabove rotating plates have the property of repelling the liquid.

[0011] By means of this invention, a magnetic circuit is constituted inthe yoke enclosing the magnet, so that the magnetic field isconcentrated at the magnetic pole surfaces, and in addition a magneticfield, of magnitude substantially equal to that at the magnetic polesurface, can be generated at the aperture side face as well.

[0012] The yoke is formed into a cup shape enclosing each of the magnetsand is mounted onto each of the rotating plates, so that compared withthe above-described conventional magnetic separation device in which a“U”-shaped yoke is positioned spanning two magnets, the amount of use ofyokes in the magnetic separation device of this invention is greatlyreduced. As a result, the weight of the magnetic separation device canbe reduced and product costs can be lowered, and in addition, runningcosts can be reduced through the reduction in weight of movable parts.

[0013] By forming a groove in the aperture side face of the yoke, themagnetic gradient is heightened in the angular portions of the groove,so that large amounts of magnetic material can adhere.

[0014] The details and other features and merits of this invention willbe made clear in the remainder of the specification, and will beillustrated in the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a cross-sectional view of a magnetic separation deviceto which this invention is applied.

[0016]FIG. 2 is a cross-sectional view along line A-A in FIG. 1 of amagnetic separation device to which this invention is applied.

[0017]FIG. 3 is a partial cross-sectional view of a magnetic separationdevice to which this invention is applied.

[0018]FIG. 4 is an enlarged cross-sectional view of a magnet and yoke ofa magnetic separation device to which this invention is applied.

[0019]FIG. 5 is a drawing showing the state of distribution of magneticlines of force created by a magnet and yoke of this invention, when thedistance between opposing magnets is large.

[0020]FIG. 6 is a drawing showing the state of distribution of magneticlines of force created by a magnet and yoke of this invention, when thedistance between opposing magnets is small.

[0021]FIG. 7 is a drawing showing the state of distribution of magneticlines of force created by a magnet and yoke of the prior art, when thedistance between opposing magnets is small.

[0022]FIG. 8 is a drawing showing the state of distribution of magneticlines of force created by a magnet and yoke of the prior art, when thedistance between opposing magnets is large.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Referring to FIG. 1 and FIG. 2, the magnetic separation device 1comprises an upstream container 2, solid-liquid separation container 3,and downstream container 4. A liquid containing magnetic suspendedmaterial flows into the upstream container 2 from an inlet 5. While thisliquid passes from the upstream container 2 to the solid-liquidseparation container 3 and flows into the downstream container 4,magnetic suspended material is separated from the liquid. Thereafter,the liquid flows out from an outlet 6 in the downstream container 4.When the inlet 5 and outlet 6 are connected to a machine tool viapiping, not shown, the machining liquid of the machine tool iscirculated to the magnetic separation device 1.

[0024] The upstream container 2 and solid-liquid separation container 3are formed integrally. From the bottom portion 2 a of the upstreamcontainer 2 to the bottom portion 3 a of the solid-liquid separationcontainer 3, the bottom portion is continuously sloped, and magneticsuspended material in the upstream container 2 is guided toward thesolid-liquid separation container 3.

[0025] The solid-liquid separation container 3 contains two rotatingplates 7, 8 forming a pair. Each of the rotating plates 7, 8, having adisc shape, is fixed to a first rotation shaft 9, and between therotating plates 7, 8 is formed a magnetic space 18 in which a magneticfield is generated by a plurality of magnets 13. Each of the rotatingplates 7, 8 is perpendicular to the direction of the rotation shaft. Therotating plates 7, 8 are formed from a nonmagnetic material, and on theback faces 17 of each are mounted a plurality of permanent magnets 13.In this aspect, the number of permanent magnets is six. The rotatingplates 7, 8 rotate while approximately half of each rotating plate isimmersed in the liquid collected in the solid-liquid separationcontainer 3. Magnetic material suspended in the liquid adheres to theadhesion surfaces 16 of the rotating plates 7, 8 as a result of themagnetic force of the magnets 13.

[0026] As means to have the liquid flow through the magnetic space 18,an aperture portion 32 opposing the magnetic space 18 is formed in thepartition wall 31 which separates the upstream container 2 from thesolid-liquid separation container 3. An aperture portion 34 opposing themagnetic space 18 is formed in the partition wall 33 which separates thesolid-liquid separation container 3 from the downstream container 4. Theaperture portions 32, 34 have substantially the same width as themagnetic space 18, and are such that the main flow of the liquid flowingthrough the solid-liquid separation container 3 passes through themagnetic space 18. Consequently despite the fact that liquid flowsaround the backs of each of the rotating plates 7, 8 of the solid-liquidseparation container 3, the main flow of the liquid passes through themagnetic space 18, and most of the magnetic suspended material adheresto the adhesion surfaces 16.

[0027] Referring to FIG. 3, a plurality of magnets 13 are fastened atequal intervals in the circumferential direction to the back surface 17of each of the rotating plates 7, 8. The magnets 13, provided in pairsand opposing one another across the rotating plates 7 and 8, arepositioned with opposing magnetic poles (the N pole and S pole) inopposition. In this aspect, the N poles of the magnets 13 abut the backsurface 17 of the rotating plate 7, and the S poles of the magnets 13abut the back surface 17 of the rotating plate 8. An arrangement inwhich N poles and S poles of the magnets 13 alternately abut one backsurface 17 is also possible.

[0028] Referring to FIG. 4, the magnets 13 and yokes 14 comprised by themagnetic separation device 1 are explained. The yoke 14 has a cup-likeform (a concave shape), and accommodates a magnet 13. That is, the yoke14 has an aperture facing one of the magnetic poles of the magnet 13,and surrounds the magnet 13. This yoke 14 comprises a cylindrical sidewall portion 14 a. The yoke 14 has an end wall portion 14 b, which isjoined to one end of the side wall portion 14 a and abuts one magneticpole of the magnet 13, and an aperture side face 14 c which opposes andsurrounds the other magnetic pole of the magnet 13. The magnet 13 is incontact with the inner surface of the yoke 14, without a gap.

[0029] The side wall portion 14 a and end wall portion 14 b havecross-sectional areas in response to the saturation flux density of themagnet 13, to constitute a magnetic circuit. In this aspect, acylindrical magnet 13 and cylindrical yoke 14 are used; but thecross-sectional shapes of the magnet 13 and yoke 14 need not becircular, and may be polygonal or rectangular.

[0030] The yoke 14 is mounted such that the aperture side face 14 c andthe magnetic pole face of the magnet 13 are in contact with the backsurface 17 of one of the rotating plates 7, 8. A strong magnetic fieldoccurs at the sites of contact of the magnetic pole faces of the magnets13 and aperture side faces 14 c on the back surfaces 17 of each of therotating plates 7, 8, so that the adhesion surfaces 16 can causeadhesion of magnetic suspended material.

[0031] The yoke 14 is formed from ferromagnetic material, to constitutea magnetic circuit. In this aspect, magnets having a strong magneticforce, such as for example ferrite magnets, rare-earth magnets or otherpermanent magnets, are used as the magnets 13; however, electromagnetscomprising electromagnetic coils may also be used.

[0032] A plurality of grooves 19 with “U”-shaped depressions are formedin ring shapes in the aperture side face 14 c of the yoke 14. In thisaspect, there are two grooves 19. Because each groove 19 is open on theaperture side face 14 c, the yoke 14 has a number of angular portionsequal to twice the number of grooves 19, in addition to the angularportions of the inner and outer perimeters of the side wall portion 14a. Hence in this aspect, the magnetic gradient can be raised at a totalof six angular portions, so that a large amount of magnetic suspendedmaterial can be made to adhere.

[0033] The yokes 14 shield the magnetic field behind each of therotating plates 7, 8, so that magnetic suspended material does notadhere to the yokes 14. Consequently the occurrence of a largeresistance to the rotations of the rotating plates 7, 8 can be avoided.

[0034] Because the yokes 14 formed from ferromagnetic material surroundthe magnets 13 to constitute a magnetic circuit providing a path formagnetic force lines, the magnetic field is concentrated at the magneticpole surfaces. Simultaneously, a magnetic field of substantially thesame magnitude as at the magnetic pole surfaces also occurs at theaperture side faces 14 c.

[0035] As shown in FIG. 5, when two magnets 13 with opposite polesopposing are at a distance such that one magnet does not exert amagnetic action on the other magnet, a magnetic circuit is constitutedfor each magnet 13 via the yoke 14. In this case, magnetic lines offorce connecting the magnetic pole surface and the aperture side face 14c pass through the magnetic space 18, and thus the strength of themagnetic field occurring at the pole faces is substantially twice asgreat as that of individual magnets 13.

[0036] As shown in FIG. 6, when two magnets 13 with opposite polesopposing are at a distance such that one magnet exerts a magnetic actionon the other magnet, a magnetic circuit connecting the two magnets 13via the yoke 14 is constituted. In this case, magnetic lines of forceconnecting the opposing poles of the magnets 13 cross through themagnetic space 18. Similarly, magnetic lines of force connecting theopposing aperture side faces 14 c of the yokes 14 cross through themagnetic space 18, and thus the strength of the magnetic field occurringat pole faces is substantially four times that of the individual magnets13.

[0037] In this way, in the yokes 14 of this invention, the magneticfield occurring at the adhesion surface 16 is strengthened, and theadhesion area of the adhesion surface 16 over which the magnetic fieldextends is increased, so that magnetic suspended material flowingthrough the solid-liquid separation container 3 efficiently adheres tothe rotating plates 7, 8. Consequently the magnetic separation device 1of this invention can greatly reduce the amount of magnetic suspendedmaterial remaining in the liquid. When applying this invention togrinding equipment, by raising the degree of cleaning of the machiningfluid, the machining precision can be improved. And, in such casesreduction of the efficiency of cutting and grinding by bits and grindingelements in the equipment can be prevented, and the lifetimes of themachining fluid and grinding elements can be extended.

[0038] By strengthening the magnetic field occurring at the adhesionsurface 16, the magnetic suspended material which magnetically adheresto the adhesion surface 16 grows in chainlike fashion, and moves in theliquid together with the rotating plates 7, 8. In this case, carbon andother nonmagnetic suspended material are also drawn out from the liquidtogether with magnetic suspended material, and are recovered.Consequently when the liquid is the machining fluid of grindingequipment or similar, the anaerobic bacteria in the machining fluid areremoved. In addition, magnetic bacteria having magnetic members(magnetite) are also recovered together with suspended material throughthe action or the strong magnetic field. In this way, a putrid smell ofthe machining fluid or other liquid due to the occurrence of bacteriacan be eliminated.

[0039] As shown in FIG. 2, the magnetic separation device 1 comprises ascraper 21 which rotates moving through the magnetic space 18 betweenthe rotating plates 7, 8. This scraper 21 scrapes away magneticsuspended material adhering to both the adhesion surfaces 16 whilesliding in contact with the adhesion surfaces 16 of the rotating plates7, 8. The scraper 21 is formed from rubber material, and the baseportion is fixed to a second rotation shaft 22.

[0040] This second rotation shaft 22 rotates, in synchronization withthe rotating plates 7, 8, in response to the first rotation shaft 9 bymeans of a rotation transfer device. As shown by arrows in FIG. 2, therotating plates 7, 8 rotate in the clockwise direction, and the scraper21 rotates in the counterclockwise direction. During the period in whichthe rotating plates 7, 8 make one revolution, the scraper 21 rotates, insynchronization with this, a number of times equal to the number ofmagnets 13 on a rotating plate.

[0041] The scraper 21 scrapes magnetic suspended material adhering toeach of the adhesion surfaces 16 at the positions of installation ofeach magnet 13 into the side of the downstream container 4. The scraper21 rotates in the direction opposite the rotating plates 7, 8 to scrapeaway suspended material which magnetically adheres to the adhesionsurfaces 16. In this way, the scraped-away suspended material isprevented from again adhering to areas to which the magnetic field ofthe magnets 13 extends. And, by mounting two scrapers 21 in common onthe second rotation shaft 22 at an angular separation of 180°, the rateof rotation of the second rotation shaft 22 can be reduced to half.

[0042] Above the scraper 21, a scrape-away plate 23 is hung in arotatable fashion from a shaft 24. By means of gravity, the scrape-awayplate 23 scrapes away magnetic suspended material and similar attachedto the scraper 21 while making contact with the scraper 21.

[0043] Below the scraper 21, a receiver portion 25 which collects themagnetic suspended material which has been scraped away, and a dischargepath 26 to discharge the magnetic suspended material collected in thereceiver portion 25, are provided. The receiver portion 25 is bent in anarc shape along the path through which the tip of the scraper 21 moves.Magnetic suspended material collected in the receiver portion 25 istransported to the discharge path 26 by the scraper 21. This magneticsuspended material slides and drops into the discharge path 26, and isrecovered in a retention container 27 provided outside.

[0044] The adhesion surfaces 16 of the rotating plates 7, 8 have theproperty of repelling water, machining fluid, or other liquids.Consequently liquid, which is attached to the adhesion surfaces 16 andrises above the liquid surface by the rotation of the rotating plates 7,8, is drawn by the adhesion surfaces 16, and is rapidly returned to thesolid-liquid separation container 3. In this way, the carrying of liquidoutside the solid-liquid separation container 3 is impeded. In thisaspect, each of the rotating plates 7, 8 is formed integrally from aresin having the property of repelling liquids. Each of the rotatingplates 7, 8 may also be formed from stainless steel plates not havingmagnetic properties, and surface treatment then performed to endow theadhesion surfaces 16 with the property of repelling liquids.

[0045] The magnetic separation device 1 may also comprise in parallel aplurality of sets of rotating plates 7, 8, each comprising magnets, inorder to accommodate increases in flow volume.

[0046] This invention is not limited to the above aspect, and variousmodifications may be made within the scope of the technical concept.

1. A magnetic separation device, comprising: two rotating plates whichare fixed to a rotation shaft and rotate while immersed in a liquid; andone or more magnets mounted on each of the rotating plates and causingmagnetic adhesion of magnetic material in said liquid to each of saidrotating plates to perform separation; each of said magnets comprising ayoke which has an aperture facing one magnetic pole and surrounds saidmagnet, said one magnetic pole contacting one rotating plate; said yokecomprising an aperture side face in contact with said one rotatingplate; wherein a pair of magnets is positioned such that oppositemagnetic poles oppose each other across said two rotating plates to forma magnetic space between said two rotating plates.
 2. The magneticseparation device according to claim 1, wherein a “U”-shaped groove isformed in said aperture side face.
 3. The magnetic separation deviceaccording to claim 1, further comprising a scraper which scrapes awaymagnetic material attached to said rotating plates, and a mechanismwhich rotates said scraper in synchronization with said rotating plates.4. The magnetic separation device according to claim 1, wherein thesurfaces of said rotating plates have the property of repelling liquid.5. The magnetic separation device according to claim 1, furthercomprising means for guiding said liquid in said magnetic space.